AhR (Aryl hydrocarbon receptor)

Nuclear receptor present in keratinocytes and Langerhans cells. It is activated by microbial tryptophan metabolites (indoles) produced by gut bacteria, as well as by dietary polyphenols. It regulates skin barrier immunity. Its dysfunction is implicated in atopic dermatitis and psoriasis, constituting a direct molecular link between the gut microbiome and the skin.